Eosinophilic endomyocardial fibrosis is a common and often lethal complication of both the idiopathic hypereosinophilic syndrome and eosinophilla secondary to certain neoplastic and tropical diseases. Recent work suggests that the cardiovascular damage is mediated by cationic proteins found in the eosinophil's specific granules; the mechanisms by which these proteins induce myocardial and endocardial damage are not known. In accordance with the educational and research goals of the Physician Scientist Award, the plan is divided into two phases. n phase I, the basic science skills of the principal investigator will be updated in the areas of cell and molecular biology. cDNA clones for the eosinophil cationic protein, the eosinophil granule major basic protein and the eosinophil-derived neurotoxin will be isolated and sequenced. Once this has been accomplished, phase II will introduce more complex recombinant DNA techniques. The cDNA clones will be introduced into prokaryotic or eukaryotic systems permitting the expression of the recombinant proteins; the recombinant proteins will be purified and evaluated for their ability to bind to and /or damage myocardial and endothelial cells in culture. In vitro mutagenesis will be used to introduce defined sequential deletions and point mutations into the cDNA sequences, and mutant recombinant eosinophil proteins unable to carry out binding and/or cytotoxicity will be identified. These experiments aim to identify functionally significant amino acid sequences and to clarify the mechanisms by which the eosinophil granule proteins interact with their cardiovascular targets. From an educational perspective, the planned program will provide the skills and experience necessary for the principal investigator to pursue a career as an independent clinician-scientist.